Printed circuit boards (PCBs) are widely used in most electronic products. The manufacturing of PCBs is considered cheaper, faster and more accurate than using other wiring methods such as point-to-point construction. Still, there is an ongoing search for simpler and more cost-effective manufacturing processes that would maintain high quality and would enable to produce PCBs according to specific requirements including the manufacturing of cost-effective smaller batches, larger batches with high throughput, on-demand boards, boards with denser wiring, boards with thinner wires and others.
The wiring pattern in the manufacturing of a PCB is usually done by subtractive methods that involve removing copper from a copper layer laminated to an insulating material board, leaving only the desired copper wire (also refer to as pattern or image) as the electrically conducting paths. The process includes applying an etch-resist mask on the copper layer and removing exposed copper portions by an etching process. The current commonly used method for preparing the etch resist mask involves coating the copper layer with photosensitive etch-resist substance (generally, UV light sensitive substance); preparing a photo mask using, for example, photo plotter or laser plotter; exposing the layer to UV radiation to cure and fix the exposed areas as a pattern on top of the copper layer; and removing the unexposed etch-resist by chemical development. Only then, the wiring pattern can be produced by etching the unmasked copper portions following by a striping process for removing the etch-resist mask. The wiring pattern covers approximately 25% of the board's surface. During the production, however, the entire board is coated with the photosensitive etch-resist substance, followed by exposing the wiring pattern to UV or other radiation to form the etch-resist mask. The remaining photosensitive etch-resist substance is washed away.
The etch-resist pattern can also be applied by additive methods, for example by nonimpact printing (e.g. inkjet printing) on the copper layer. Conventional inkjet materials have relatively low viscosity and accordingly when ink drops would hit a non-absorbing surface, such as a copper surface, uncontrolled spreading of the drops and other phenomena such as clustering, coalescence and extensive dot gain usually occur. Accordingly, the printed pattern may exhibit reduced resolution, lack of details, inconsistent patterned line width, poor line edge smoothness, shorts between adjacent conductive lines and disconnection of pattern lines.
It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements.